Birthday is a 24 year old bank robber. After a total of 64 successful heists, she was finally caught by law enforcement. Awaiting her sentence of the death penalty, Birthday was given the offer of parole if she joined the Zero-Cops in their mission to take down the GiganTech Cybertron Corporation.
Birthday accepts the mission, and joins the "Criminal Team", which features Adam - an assassin-for hire, and Tag-T - the leader of a street bike gang. Upon defeating the evil corporation, however, Birthday returns to and embraces a life of crime. Now with a family, continues to rob banks along with her husband and four children.
Whenever someone inquired when her birthday was, she always replied "Today." That is how she earned her nickname.
Birthday's motorbike is actually her husband, Romero, who had 80% of his body mechanized.
Birthday appears as a playable guest character in the 2000 arcade shooter "Dimahoo".